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If you go to a gym, you’ve probably heard the guys by the weight machines talking about the protein shakes they drink after a workout and what kind of shake they prefer. Protein powders -- made into a shake or consumed however you like -- are getting more and more popular as a nutritional supplement.

You can buy protein powders in every nutrition store and all over the Internet. You can even find pre-mixed, ready-to-drink protein shakes in many stores. But are protein powders just for bodybuilders, or can the average everyday athlete benefit from them as well?

What Are Protein Powders?

Protein powders come in various forms. The three common ones are whey, soy, and casein protein. “Whey is the most commonly used, because it’s a water-soluble milk protein,” says Peter Horvath, PhD, associate professor in the department of exercise and nutrition sciences at the State University of New York at Buffalo. “It’s also a complete protein, so it’s got all those advantages.” (Complete proteins contain all nine of the amino acids necessary for human dietary needs.) People who are vegan may prefer soy protein, although Horvath notes that its taste is sometimes considered to be more unpleasant, and it doesn’t dissolve as well in water.

Protein powders also come with widely varying price tags. “For the casual athlete who doesn’t have a specific need at a certain time of their training, the cost is not that important,” says Horvath. “So if you’re going to use them, you can get pretty much the same benefit out of the less expensive, more commercially available proteins.

In very specific circumstances, protein powders can be useful. “They’re an easy and convenient source of complete, high-quality protein,” says Carole Conn, PhD, RD, CSFD, associate professor of nutrition at the University of New Mexico. But remember: Most people, even athletes, can also get everything they offer by eating sources of lean protein like meat, fish, chicken, and dairy products.

So when might you want to use them? There are a few reasons why an ordinary athlete might want more protein in their diet, says Barbara Lewin, RD, LD, a dietitian and sports nutritionist who has worked with NFL, NBA, and NHL athletes and trained Ironman competitors:

When you’re growing. A teenager needs more protein to fuel his workouts because his body is still growing and uses more protein in general.

When you’re starting a program. If working out is new to you and you’re trying to build muscle, you’ll require more protein than you normally would.

When you’re amping up your workouts. If you normally work out for half an hour a few times a week, but now you’ve decide to train for a half-marathon, your body will need more protein.

When you’re recovering from an injury. Athletes with sports injuries frequently need more protein to help them heal.

If you’re going vegan. People who pursue a vegan or vegetarian lifestyle eliminate a number of common protein sources from their diet, including meat, chicken, and fish, and sometimes dairy and eggs as well.

“All of those are valid reasons for trying to get more protein into your diet, and protein powders are one way to do that,” says Lewin.

But there’s a big caveat, Lewin adds: it doesn’t take that much protein to achieve those goals. Most Americans already get about 15% of their daily calories in protein. To build a pound of muscle, Lewin explains, the body needs between 10 and 14 additional grams of protein per day.

“That’s not really that much. Some of these powders have 80 grams of protein per serving. You don’t need that. All your body is going to do is break it down for energy. And too much protein can be hard on your kidneys and your liver.”

Protein Math

So how can you tell if you’re already getting enough protein? Do the math.

Recreational athletes need 0.5-0.75 grams of protein daily for every per pound of body weight

Competitive athletes need 0.6-0.9 grams per pound

Teenage athletes need 0.8-0.9 grams per pound

Athletes building muscle mass need 0.7-0.9 grams per pound

The maximum amount of protein that most adults can use per day is 0.9 grams per pound of body weight.

So if you’re an adult athlete who wants to build muscle mass, and you weigh about 175 pounds, the most protein you would need per day is 157.5 grams. That sounds like a lot, but one 4-ounce hamburger contains 30 grams of protein, 6 ounces of tuna has 40 grams, and a single ounce of cheddar cheese has 7 grams. (To find a list of foods with their protein content, use the U.S. Department of Agriculture’s Nutrient Database, online at www.ars.usda.gov/Services/docs.htm?docid=20958.)

How to Use Protein Powders

If you calculate your protein intake and determine that you’re notgetting enough for your athletic needs (some signs of too-low protein intake: you’re unusually fatigued, feel weak when lifting weights or doing other strenuous activity, or are recovering from injuries slowly) how can you best use protein powders to help you improve your performance?

First, ignore the conventional wisdom, which says to take protein powders immediately after a workout. “Before, during, and after a workout, carbs are what your body needs. They’re what your body uses for fuel, and what your muscles run on,” says Lewin. “Yes, protein is also important for recovery after a workout, but research shows that at that point, the body needs fuel with a 4-1 or 5-1 ratio of carbs to protein.” Since most protein powders have at least 20 grams of protein per scoop, you’d need about 80 grams of carbs to go with that scoop to get the proper proportion of nutrients!

For a better “recovery drink” after a workout, Lewin recommends a fruit smoothie with yogurt or milk, or, surprisingly, chocolate milk. “A glass of chocolate milk is one of the best things for recovery,” she says.

So when should you use protein powders, if you’ve determined you need them to get more protein in your diet? Throughout the day as a snack or meal replacement, says Lewin, but not in the immediate time period surrounding your workouts.

And don’t forget, says Conn: “Protein powders are not really necessary if you have access to a normal, healthy diet.”